Name request log actions so they say what they mean (closes #229)

The request log's `action` values now say what they mean, as sneak named them: `request_header_too_large`, `client_is_rate_limited`, `blocked_by_block_rule` and `client_denied`, with no aliases. `banned` splits into `temporarily_banned` and `permanently_banned`, by whether the ban runs out. When a permanent ban also covers a client, that ban is the one reported.

Trips a reader: a request over a rate limit stays `client_is_rate_limited` even when the ban it makes is permanent.
Disclosure: the offence key `rule_blocked` is renamed in `clients.json` too, so an existing file holding it stops the start and must be removed. Its `version` stays 1.

Model: opus-5-5

internal/discriminator/admin_test.go

@@ -121,7 +121,7 @@ func TestBanAddedListedAndLiftedThroughTheEndpoints(t *testing.T) {
 	wantBans(t, s.admin(http.MethodPost, discriminator.BansPath, banOtherClient,
 		http.StatusOK), want)
 
-	line := s.get(client, http.StatusForbidden, requestlog.ActionBanned)
+	line := s.get(client, http.StatusForbidden, requestlog.ActionTemporarilyBanned)
 	if line.BanExpires != requestlog.FormatTime(expires) {
 		t.Errorf("the ban ends at %s, want %s", line.BanExpires, expires)
 	}
@@ -276,7 +276,7 @@ func TestClientEndpointShowsTheClientAndItsBans(t *testing.T) {
 	// limit of two a minute, and bans it.
 	s.get(otherClient, http.StatusOK, requestlog.ActionForward)
 	s.get(otherClient, http.StatusOK, requestlog.ActionForward)
-	s.get(otherClient, http.StatusForbidden, requestlog.ActionRateLimited)
+	s.get(otherClient, http.StatusForbidden, requestlog.ActionClientIsRateLimited)
 
 	// Asked about by its address in IPv6 form too.
 	for _, addr := range []string{otherClient, "::ffff:" + otherClient} {